There are measuring apparatuses which are used to measure the geometry, properties and other aspects of workpieces by means of measuring probes. Such measuring apparatuses are frequently used for measuring gearwheels and similar workpieces.
It is relevant in such measuring apparatuses to guarantee high measuring precision. Therefore, a respective amount of work is invested in order to design all relevant components of such measuring apparatuses in such a way that the measuring errors are low.
In order to reach any desired point in the three-dimensional space with the measuring probe, the measuring apparatus should have three or more numerically (CNC) controlled axes.
Different problems arise in connection with large, bulky and very heavy workpieces which do not allow scaling existing measuring apparatuses in a respective manner, like the prior known apparatus as shown in FIG. 1 for example. The weight of the workpieces is especially problematic because a deformation of the machine bed or the measuring table may occur in conventional measuring apparatuses when the same is not provided with sufficient stiffness for example. This deformation leads to imprecision in the measurement which cannot be tolerated.
A portal-type measuring apparatus is known from the German patent specification DE 10 2005 058 504 B3 which comprises a measuring probe which can be moved in all spatial directions of a Cartesian system of coordinates. The object to be measured rests on a table which stands on a foundation or base by means of several special feet. The measuring probe is moved by means of a portal-like frame over the object and along the table. By vertically lowering the measuring probe, the object can be scanned from above. This patent specification offers a solution which allows reducing the influence of weight on the positional and measuring precision.
It is a disadvantage of this arrangement however that as a result of the clearance height of the portal-like frame the maximum height of the object to be measured is limited as also the width by the clearance width. Moreover, there are numerous workpieces which, as a result of their geometry, cannot be measured on such a portal-type measuring apparatus in the horizontal position or can only be measured within limits. Furthermore, the described portal-type measuring apparatus comes with the disadvantage that the vertical adjustability which is promoted as a relevant feature will no longer work or work only within limits in the case of workpieces of high weight.
It is a further disadvantage of this solution that the amount of work or distance for displacement of the measuring probe is relatively large and thus the measuring duration is long when rotationally symmetrical workpieces (such as gearwheels for example) need to be measured.
It is therefore an object of the invention to provide a measuring apparatus and a novel workpiece receiver which allows measuring large and especially heavy workpieces in a rapid and reliable way without the weight of the workpiece having a negative influence on the measuring precision.
Moreover, the apparatus shall be inexpensive to produce and still measure in a highly precise manner.